Three-dimensional electrochemical-thermal coupling simulation system for internal short circuit of lithium metal battery

Abstract

The invention discloses a three-dimensional electrochemical-thermal coupling simulation system for lithium metal battery internal short circuit, and belongs to the technical field of lithium ion battery simulation modeling and safety design. In order to solve the problem that a multi-field coupling mechanism and spatio-temporal evolution characteristics of a lithium dendrite induced internal short circuit are difficult to reveal in the prior art, a high-fidelity simulation platform of electrochemical-thermal-short circuit multiple physical field bidirectional coupling is established by constructing and integrating a three-dimensional battery model of a lithium dendrite geometry with size and position parameters capable of being defined. The system can accurately calculate current distribution, voltage drop, temperature field evolution and heat production rules in the internal short circuit process, different short circuit scenes are simulated through parameterization setting, and quantitative comparison and risk study and judgment of internal short circuit characteristics are achieved. The invention provides an advanced tool for researching the short circuit mechanism in the lithium metal battery, obviously reduces the research and development cost and period, and has important guiding significance for improving the safety of the high-energy-density battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery simulation modeling, and specifically to a three-dimensional electrochemical-thermal coupling simulation system for internal short circuits in lithium metal batteries. Background Technology

[0002] Energy is a core driver of national economic development and is closely related to social operations and daily life. In recent years, the development and utilization of clean and renewable energy have progressed rapidly, gradually reducing dependence on traditional fossil fuels. Lithium-ion batteries, due to their advantages such as high energy density, long cycle life, and high safety, have become one of the most important secondary energy storage systems, widely used in new energy vehicles, small drones, aerospace, and large-scale energy storage stations. However, the energy density of currently commercially available lithium-ion batteries is gradually approaching the theoretical upper limit of embedded electrode materials (such as graphite anodes), and further significant improvements in energy density urgently require system-level innovation.

[0003] Lithium metal anodes are considered key materials for realizing next-generation high-energy-density battery systems due to their extremely high theoretical specific capacity (3860 mAh / g, approximately 10 times that of graphite) and low electrochemical potential (-3.04 V vs. standard hydrogen electrode). When matched with high-capacity cathodes (such as lithium-rich manganese-based or nickel-cobalt-manganese ternary materials), the energy density of lithium metal batteries is expected to exceed 400 Wh / kg. Nevertheless, the practical application of lithium metal batteries still faces severe challenges, mainly in terms of poor cycle stability and prominent safety issues. During battery cycling, lithium dendrites easily form unevenly deposited lithium on the lithium metal surface. Their continuous growth can puncture the separator, causing internal short circuits. Simultaneously, the deposited lithium reacts with the electrolyte to produce "dead lithium," leading to rapid capacity decay and reduced coulombic efficiency. Internal short circuits caused by lithium dendrites are a common cause of thermal runaway, seriously threatening battery system safety and becoming the primary technical obstacle restricting the commercial application of lithium metal batteries.

[0004] Currently, research on lithium dendrites and internal short-circuit behavior still heavily relies on experimental methods, which have limitations such as long testing cycles, high costs, high destructiveness, and difficulty in real-time observation of internal reactions and thermal evolution. Traditional experimental methods cannot fully reveal the multi-field coupling mechanisms and spatiotemporal evolution characteristics during internal short circuits, thus hindering a deeper understanding of battery failure mechanisms and the establishment of safety design criteria. Although some simulation models have been used in battery research, most are limited to a single physical field or simplified two-dimensional structures, making it difficult to realistically reflect the internal short circuits induced by lithium dendrites and the complex electrochemical-thermal coupling behavior they trigger. Summary of the Invention

[0005] To address the shortcomings of existing experimental methods in revealing the multi-field coupling mechanism and spatiotemporal evolution behavior of internal short circuits, and the limitations of existing simulation models in terms of multidimensional coupling and geometric realism, this invention provides a three-dimensional electrochemical-thermal coupling simulation method for the internal short circuit behavior of lithium metal batteries. This system constructs a three-dimensional battery model with a lithium dendrite structure whose geometric and positional parameters can be defined to realistically simulate the positive-negative electrode internal short circuit process caused by lithium dendrites piercing the separator. Based on the electrochemical-thermal-short circuit multi-coupling mechanism, it calculates and analyzes the dynamic changes of key physical quantities such as electrode current density distribution, voltage change, temperature field evolution, and internal heat generation during the internal short circuit process. By flexibly setting the radius and spatial position parameters of lithium dendrites, it achieves quantitative comparison and hazard level assessment of different internal short circuit scenarios. This invention provides an efficient and reliable digital tool for studying the internal short circuit behavior of lithium metal batteries, significantly reducing experimental costs and development cycles, and providing theoretical basis and simulation support for the design of high-safety battery materials and the optimization of thermal management strategies.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a three-dimensional electrochemical-thermal coupling simulation system for internal short circuits in lithium metal batteries, the three-dimensional electrochemical-thermal coupling simulation system comprising:

[0007] A three-dimensional geometric model is established based on the parameters of the lithium metal battery sample to be tested. The three-dimensional geometric model includes the positive electrode, negative electrode, separator, and current collector of the battery.

[0008] The lithium dendrite geometry embedded in the three-dimensional geometric model and used to simulate physical short-circuit contacts has a radius and spatial position that can be defined parameters.

[0009] The electrochemical-thermal coupled calculation module is used to couple the following processes:

[0010] Electrochemical process: Calculate the voltage and current distribution and electrochemical heat generation of the lithium metal battery under test;

[0011] Thermal processes: Calculation of the spatiotemporal evolution of the temperature field of lithium metal batteries driven by both electrochemical heat generation and internal short-circuit ohmic heat;

[0012] Short-circuit feedback process: The internal electrochemical parameters of the lithium metal battery that change due to temperature changes are fed back to the electrochemical process in real time, and the internal short-circuit resistance and its heat generation are fed back to the electrochemical process and the thermal process.

[0013] The three-dimensional electrochemical-thermal coupling simulation system simulates and outputs data on changes in battery voltage, current density, temperature field, and heat generation power under different internal short-circuit scenarios by changing the radius and position parameters of lithium dendrite geometry. This data is used to analyze internal short-circuit characteristics and guide battery safety design.

[0014] Preferably, in the electrochemical-thermal coupling calculation module, temperature changes affect the electrochemical reaction kinetic parameters in real time through the Arrhenius relation, thereby achieving bidirectional coupling between the thermal field and the electrochemical field.

[0015] Preferably, the radius parameter of the lithium dendrite geometry is in the range of 50 μm to 150 μm, and the position parameter is selected from one of a plurality of preset positions in the battery plane.

[0016] Preferably, the parameter initialization and calibration of the three-dimensional geometric model and the electrochemical-thermal coupling calculation module are based on data obtained from electrochemical and thermal tests on real lithium metal battery samples, electrode samples, and material samples to be tested. The data includes one or more of the following: geometric parameters, solid / liquid phase conductivity, lithium ion diffusion coefficient, reaction rate constant, specific heat capacity, and thermal conductivity.

[0017] Preferably, when meshing the target region containing lithium dendrite geometry, the meshing strategy is as follows: first, perform consistent meshing on the contact surfaces between the lithium dendrite geometry and the positive and negative electrodes, and then refine the entire target region into a free tetrahedral mesh.

[0018] Secondly, the present invention provides a method for simulating the internal short-circuit behavior of a lithium battery using the above-mentioned three-dimensional electrochemical-thermal coupling simulation system, comprising the following steps:

[0019] Step 1: Obtain the physicochemical parameters of a real lithium battery sample, and initialize the parameters of the three-dimensional electrochemical-thermal coupling simulation system accordingly;

[0020] Step 2: Define the initial radius and initial spatial position parameters of the lithium dendrite geometry in the three-dimensional electrochemical-thermal coupling simulation system, run the simulation system, and obtain simulation data under the initial internal short circuit scenario;

[0021] Step 3: Change the radius and spatial position parameters of the lithium dendrite geometry, run the simulation system, and obtain simulation data for at least one modified internal short-circuit scenario;

[0022] Step 4: Compare and analyze the simulation data obtained in Step 2 and Step 3 to evaluate the risk level of internal short circuit caused by lithium dendrite geometry under different parameters.

[0023] Thirdly, the present invention provides a lithium battery safety design method, which optimizes the lithium battery based on the hazard level and parameters obtained by the above method.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. This invention constructs a full-scale three-dimensional geometric model based on real battery sample parameters. Combined with the unique meshing strategy designed in this invention, which features consistent meshing of lithium dendrites and positive and negative electrode contact surfaces and local free tetrahedral refinement, it not only ensures the geometric authenticity of the battery structure and the spatial distribution of lithium dendrites, but also accurately captures the abrupt changes in key physical quantities such as current density and heat generation power at short-circuit contacts. This significantly improves the fit between simulation results and real operating conditions, and effectively solves the technical pain points of existing simplified three-dimensional models being unable to cover complex short-circuit scenarios and insufficient calculation accuracy in key areas.

[0026] 2. The innovative electrochemical-thermal-short-circuit triple coupling mechanism constructed in this invention achieves bidirectional feedback between the thermal and electrochemical fields through the Arrhenius relation. Simultaneously, it feeds back the short-circuit resistance and ohmic heat in real time to the multiphysics calculation process, fully restoring the chain evolution mechanism of internal short circuits: "electrochemical heat generation - temperature rise - reaction acceleration - short-circuit enhancement - ohmic heat surge". This breaks through the limitation of traditional unidirectional coupling models that cannot reveal deep coupling mechanisms. It can simultaneously output multi-dimensional dynamic data such as voltage response, spatiotemporal evolution of temperature field, and heat generation power distribution, providing quantitative support for the study of internal short-circuit mechanisms.

[0027] 3. Based on the flexible and adjustable characteristics of lithium dendrite parameters and the standardized process of "parameter initialization - multi-scenario simulation - comparative analysis - hazard assessment", this invention can systematically carry out simulation comparisons under different short-circuit conditions, establish a quantitative assessment standard for internal short-circuit hazard levels, fill the gap of existing technologies that can only qualitatively analyze parameter correlations and cannot provide accurate decision-making basis for safety design, and provide targeted theoretical guidance for battery material selection, internal structure optimization and thermal management strategy customization.

[0028] 4. The simulation system described in this invention is not a simple simulation model, but an industrial-grade research tool that integrates accurate modeling, coupled calculation, result analysis, and design support. It can obtain in-depth mechanism data without relying on high-risk and high-cost repeated experiments, which greatly reduces the cycle cost and safety risks of battery safety research and development. It provides efficient and reliable technical support for the industrialization of high-energy-density lithium metal batteries and has significant engineering application value and economic value. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the overall process of the present invention.

[0030] Figure 2 This relates to the electrochemical-thermal coupling principle in this invention.

[0031] Figure 3This diagram illustrates the arrangement of lithium dendrites, the geometry of the three-dimensional electrochemical-thermal coupling of the lithium metal battery, and its mesh division in this invention. Specifically, a represents the arrangement of lithium dendrites, b represents the geometric structure of the lithium metal battery in the three-dimensional electrochemical-thermal coupling, and c represents the mesh division of the lithium metal battery in the three-dimensional electrochemical-thermal coupling.

[0032] Figure 4 The graph shows the changes in short-circuit voltage and electrode current density in the internal short circuit in Example 1.

[0033] Figure 5 This is a diagram showing the overall heat generation of the battery and the heat generation power of each part of the battery in Example 1; where a represents the overall heat generation of the battery and b represents the heat generation power of each part of the battery.

[0034] Figure 6 This is a graph showing the temperature change at the short circuit point on the battery surface after an internal short circuit occurs in Example 1.

[0035] Figure 7 The graph shows the changes in battery voltage, heat, and temperature under different lithium dendrite radii in Example 1.

[0036] Figure 8 The graph shows the heat and temperature changes under different lithium dendrite radii in Example 1; where a represents the heat change under different lithium dendrite radii, and b represents the temperature change under different lithium dendrite radii.

[0037] Figure 9 This is a geometric model diagram of short circuits at different locations in Example 1.

[0038] Figure 10 This is a temperature change diagram of short circuits at different locations in Example 1.

[0039] Figure 11 The following are contour maps of short circuits at different locations in Example 1; where a is the upper left, b is the center, c is the lower left, d is the lower right, and e is the lower right. Detailed Implementation

[0040] The technical solutions of the present invention will be clearly and completely described in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the present invention are within the scope of protection of the present invention.

[0041] Unless otherwise specified in the specific circumstances, the numerical ranges listed herein include upper and lower limits, as well as all integers and fractions within that range, but are not limited to the specific values ​​listed when the range is defined.

[0042] I. A three-dimensional electrochemical-thermal coupling simulation system for internal short circuits in lithium metal batteries

[0043] The three-dimensional electrochemical-thermal coupling simulation system described in this invention is constructed using finite element software. The simulation system includes:

[0044] A three-dimensional geometric model is established based on the parameters of the lithium metal battery sample to be tested. The three-dimensional geometric model includes the positive electrode, negative electrode, separator, and current collector of the battery.

[0045] The lithium dendrite geometry embedded in the three-dimensional geometric model and used to simulate physical short-circuit contacts has a radius and spatial position that can be defined parameters.

[0046] The electrochemical-thermal coupled calculation module is used to couple the following processes:

[0047] Electrochemical process: Calculate the voltage and current distribution and electrochemical heat generation of the lithium metal battery under test;

[0048] Thermal processes: Calculation of the spatiotemporal evolution of the temperature field of lithium metal batteries driven by both electrochemical heat generation and internal short-circuit ohmic heat;

[0049] Short-circuit feedback process: The internal electrochemical parameters of the lithium metal battery that change due to temperature changes are fed back to the electrochemical process in real time, and the internal short-circuit resistance and its heat generation are fed back to the electrochemical process and the thermal process.

[0050] The three-dimensional electrochemical-thermal coupling simulation system simulates and outputs data on changes in battery voltage, current density, temperature field, and heat generation power under different internal short-circuit scenarios by changing the radius and position parameters of lithium dendrite geometry. This data is used to analyze internal short-circuit characteristics and guide battery safety design.

[0051] In its research on existing technologies, this invention addresses the challenges of current experimental methods in revealing the deep mechanisms of multi-field coupling in internal short circuits, insufficient geometric realism in existing simulation models, simplistic coupling mechanisms, and a lack of quantitative hazard assessment capabilities. The core objectives of this invention are to accurately reproduce real-world operating conditions, elucidate coupling mechanisms, and support industrial design. First, to address the issues of insufficient geometric realism and computational accuracy, a full-scale three-dimensional model is constructed using parameters from real battery samples, with a dedicated meshing strategy designed for the critical short-circuit contact area. Second, to overcome the limitation of unidirectional coupling in reproducing chain-like evolution mechanisms, a triple-coupling system of electrochemistry, heat, and short circuit is conceived, incorporating a bidirectional feedback mechanism. Finally, to address the shortcomings of qualitative analysis in supporting safety design, a standardized multi-scenario simulation and quantitative assessment process is established. Ultimately, this invention constructs a full-scale three-dimensional geometric model containing positive and negative electrodes, a separator, and a current collector based on real battery physicochemical parameters. It employs a strategy of consistent mesh generation at the contact surfaces between lithium dendrites and positive and negative electrodes, along with localized free tetrahedral refinement. Simultaneously, it establishes a triple-coupled calculation module for electrochemistry, heat, and short circuit, achieving bidirectional feedback between the thermal and electrochemical fields through Arrhenius relation, and simultaneously incorporating real-time feedback of short-circuit resistance and heat generation. Then, a standardized process of parameter initialization, multi-scenario simulation, comparative analysis, and hazard assessment is designed, supporting flexible adjustment of lithium dendrite parameters to better adapt to and conform to actual operating conditions. Ultimately, the simulation results of the system described in this invention show significantly improved consistency with real-world conditions, fully reproducing the chain evolution mechanism of multi-field coupling in internal short circuits and simultaneously outputting multi-dimensional dynamic data. It establishes a quantitative standard for internal short-circuit hazard levels, providing accurate decision-making basis for battery material selection, structural optimization, and customized thermal management strategies. It significantly reduces R&D costs and safety risks, shortens the R&D cycle, and becomes an industrial-grade tool supporting the industrialization of high-energy-density lithium metal batteries.

[0052] In some embodiments of this invention, traditional battery thermal models typically simplify the heat source to a fixed value or rely solely on the voltage-current curve, failing to incorporate the dynamic influence of temperature on reaction kinetics into the solution loop. However, the changes during actual battery short circuits are not fixed values ​​or follow inherent curves, leading to significant differences between simulation results and reality. Therefore, this invention considers incorporating the dynamic influence of temperature on reaction kinetics, designing a system that achieves true electrochemical-thermal bidirectional coupling through real-time coupling of the Arrhenius relation and heat source feedback. This makes the system suitable for simulating strongly nonlinear and strongly coupled dynamic processes such as internal short circuits. In the electrochemical-thermal coupling calculation module of this invention, the bidirectional coupling of the thermal field and the electrochemical field is achieved through two aspects: the real-time influence of temperature on electrochemical reaction kinetic parameters and the feedback of heat generated by the electrochemical reaction on the temperature field. Figure 2As shown, the transition from the thermal field to the electrochemical field is achieved by substituting temperature into the Arrhenius relation, thus obtaining the influence on the reaction rate constant and exchange current density under this simulation scenario. The transition from the electrochemical field to the thermal field is achieved by substituting current density and overpotential into the thermal model formula, thus obtaining the evolution of the heat-driven temperature field under this simulation scenario. This closed-loop feedback mechanism enables the model to simulate the positive feedback loop of "temperature rise - intensified reaction - increased heat production - accelerated temperature rise" during internal short circuits, thereby more realistically predicting internal short circuit behavior.

[0053] In some embodiments of the present invention, the radius parameter of the lithium dendrite geometry ranges from 50 μm to 150 μm, and the position parameter is selected from one of a plurality of preset positions within the battery plane. The present invention sets the radius parameter range of the lithium dendrite geometry to 50 μm to 150 μm. This is a preferred technical choice with clear engineering significance, made based on a deep understanding of typical failure characteristics of lithium metal batteries, support from experimental data, and a feasibility trade-off in simulation practice. This size range is consistent with the size of the introduced material used in commonly used methods for simulating internal short circuits (such as implanting metal particles or laser-induced short circuits). Furthermore, the key influences on current distribution and heat transfer in the simulation can be accurately captured by the model. Because dendrites are geometrically singular regions, very fine meshing is required in the simulation. The clearly defined radius parameter range of the present invention ensures good repeatability and comparability in the simulation of the system described in this invention, laying the foundation for establishing quantitative relationships.

[0054] In some embodiments of the present invention, the parameter initialization and calibration of the three-dimensional geometric model and the electrochemical-thermal coupling calculation module are based on data obtained from electrochemical and thermal tests on real lithium metal battery samples, electrode samples and material samples to be tested. The data includes one or more of the following: geometric parameters, solid / liquid phase conductivity, lithium ion diffusion coefficient, reaction rate constant, specific heat capacity and thermal conductivity.

[0055] In some embodiments of this invention, conventional methods for handling such embedded contact problems typically generate unstructured meshes, such as free tetrahedrons, directly in three-dimensional space. This results in independently generated and mismatched mesh elements on both sides of the contact interface, forming a so-called mismatched mesh interface, ultimately leading to inaccurate calculations. In this invention, when meshing the target region containing lithium dendrite geometry, the meshing strategy is as follows: first, perform consistent meshing on the contact surfaces between the lithium dendrite geometry and the positive and negative electrodes, and then refine the entire target region using free tetrahedron meshes. This meshing strategy not only ensures the computational accuracy of the core short-circuit interface by utilizing a matched mesh, but also achieves the optimal balance between simulation accuracy and computational cost through local adaptive refinement. This meshing strategy, together with the parameterizable lithium dendrite geometry and the electrochemical-thermal bidirectional coupling mechanism proposed in this invention, constitutes an organic whole, effectively simulating the multi-field coupling mechanism and spatiotemporal evolution characteristics of internal short circuits, providing a quantitative tool for subsequent battery safety design.

[0056] II. A method for simulating the internal short-circuit behavior of lithium batteries using the above-mentioned three-dimensional electrochemical-thermal coupling simulation system.

[0057] Step 1: Obtain the physicochemical parameters of a real lithium battery sample, and initialize the parameters of the three-dimensional electrochemical-thermal coupling simulation system accordingly;

[0058] Step 2: Define the initial radius and initial spatial position parameters of the lithium dendrite geometry in the three-dimensional electrochemical-thermal coupling simulation system, run the simulation system, and obtain simulation data under the initial internal short circuit scenario;

[0059] Step 3: Change the radius and / or spatial position parameters of the lithium dendrite geometry, run the simulation system, and obtain simulation data for at least one modified internal short-circuit scenario;

[0060] Step 4: By comparing and analyzing the simulation data obtained in Step 2 and Step 3, the hazard level can be quantitatively assessed from two dimensions: dendrite size and dendrite location, revealing patterns that are difficult to obtain systematically using traditional experiments.

[0061] In practical applications, the larger the lithium dendrite radius, the higher the risk level. This is because larger lithium dendrites reduce short-circuit resistance, leading to a dramatic increase in instantaneous short-circuit current amplitude, resulting in a faster and more significant voltage drop. The heat generation is concentrated, with ohmic heat and localized reaction heat increasing linearly or quadratically with the current, creating an extremely high initial heat flux at the dendrite-electrode contact surface. The method described in this invention, when simulating extreme conditions with large-radius lithium dendrites, significantly shortens the time it takes for the battery to reach its critical temperature (e.g., separator temperature 80°C). Regarding the lithium dendrite location parameter, lithium dendrites located at the electrode edge (especially near the tab) are more dangerous than those located at the electrode center. This is because the short-circuit point at the edge / near the tab has a shorter current-current convergence path and lower equivalent resistance, attracting and withstanding a larger global current, leading to a more severe energy release. Simultaneously, the heat dissipation path at this location may be limited, making heat accumulation more likely. Therefore, the method described in this invention can accurately quantify the differences in battery "hot spot" temperature evolution at different short-circuit locations by changing the location parameters, thus identifying the most vulnerable area.

[0062] III. A Safety Design Method for Lithium Batteries

[0063] The hazard levels and parameters obtained by the method described in this invention are used to optimize lithium batteries. Specifically, simulation data can be obtained through the system described in this invention. First, it guides the selection and performance optimization of key materials. By simulating the temperature change of the separator at the short circuit, materials with high thermal stability (such as high pore-closing temperature and high melting temperature) are prioritized. In high-risk areas (such as edges) identified by simulation, high thermal conductivity coatings can be designed to rapidly diffuse local hot spots laterally; or high resistance coatings can be designed to increase the equivalent resistance of dendrite penetration and limit the short-circuit current. When analyzing internal short circuits at different locations through simulation, electrolyte additives can be optimized or artificial SEI can be designed to preferentially induce lithium deposition in areas with uniform current distribution and good heat dissipation, avoiding preferential nucleation and growth of lithium in high-risk edge areas revealed by simulation. Secondly, this invention provides guidance for the design of tabs in single cells. It can accurately display the current vector distribution and potential distribution on the current collector when short-circuited at different locations. Then, by adjusting the shape of the current collector grid, the position and number of tabs, the current distribution can be balanced, reducing the "current convergence dead zone" (high-risk area) identified in the simulation. Alternatively, in areas with higher simulated current density values, the thickness of the current collector can be increased or materials with higher conductivity can be used to reduce local ohmic heat.

[0064] Existing models studying internal short circuits typically only provide a binary conclusion of "whether thermal runaway occurs" or macroscopic voltage and temperature curves, failing to establish the relationship between "microscopic short circuit characteristics," "macroscopic battery behavior," and "design parameters." This invention, through parametric three-dimensional coupled simulation, is the first to transform battery safety design from a paradigm of "post-hoc remediation" and "trial and error" to a new paradigm of "pre-hoc prediction, mechanism-driven, and precise optimization." Distinguished from existing internal short circuit and lithium dendrite studies, this approach provides excellent design guidance in practical battery design, significantly reducing the risk of internal short circuits.

[0065] IV. Examples

[0066] Figure 1 This is a schematic diagram of the overall process of the present invention. The following embodiments will build a model and perform calculations according to this process.

[0067] Example 1

[0068] In this embodiment, a lithium metal battery is used as the research object. The positive electrode is lithium-rich manganese-based (LRMC), the negative electrode is lithium metal, and the electrolyte is lithium hexafluorophosphate (LiPF6), dissolved in a 1:1 mixture of ethylene carbonate (EC) and dimethyl carbonate (DEC) in a non-aqueous organic solvent. A model is constructed based on this real lithium battery:

[0069] (1) Electrochemical, thermal, and geometric parameters of the sample battery were obtained by conducting electrochemical and thermal tests. The battery sample used in this embodiment was a pouch battery with dimensions of 20 cm in length, 10 cm in width, and 1.6 mm in thickness. The battery tabs had dimensions of 2 cm in width and 1 cm in height. The electrochemical parameters of the battery material included the material's conductivity, the maximum and initial lithium concentrations at the cathode, the transfer number, the transport number, the Faraday constant, and the universal gas constant, as shown in Table 1. The thermal parameters of the battery material were mainly parameters related to lithium metal, as shown in Table 2.

[0070] Table 1 Electrochemical parameters of battery materials

[0071]

[0072] Table 2 Thermal parameters of lithium metal battery materials

[0073]

[0074] (2) Based on the mathematical equations of the internal reaction mechanism and thermal equilibrium relationship of lithium metal batteries, a three-dimensional electrochemical-thermal coupling model of lithium metal batteries is constructed. For the lithium metal anode, due to its dense metallic properties, the diffusion process of lithium ions in it can be ignored, and the electrochemical reaction is mainly concentrated at the electrode / electrolyte interface. Therefore, this invention adopts a simplified three-dimensional electrochemical-thermal model, considering only the reaction kinetics described by the Butler-Volmer equation and the ion transport in the electrolyte. The solid-state potential is still described by Ohm's law, but the solid-state diffusion equation is no longer considered. When constructing the thermal model, only heat conduction and heat convection are considered, while heat radiation is ignored.

[0075] mass conservation equation

[0076] ;

[0077] In the formula, D eff e c is the effective diffusion coefficient of the electrolyte. e ε represents the lithium ion concentration in the electrolyte, t represents time, and ε e The liquid phase in the porous electrode represents the volume fraction, F is the Faraday constant, j is the local current density, and t is the local current density. + This represents the lithium-ion transfer number.

[0078] Charge conservation equation:

[0079] ;

[0080] In the formula, σ eff s It is the effective conductivity of the solid phase, φ s It is solid-state potential.

[0081] The potential distribution in the electrolyte is affected by Ohm's law and the difference in lithium ion concentration:

[0082] ;

[0083] In the formula, k eff e φ is the effective ionic conductivity of the electrolyte. e Let f be the electrolyte potential, f be the mean molar activity coefficient of the electrolyte, R be the molar gas constant, and c be the mean molar activity coefficient of the electrolyte. e Where is the lithium-ion concentration of the electrolyte, and T is the battery temperature.

[0084] Electrochemical reaction kinetic equations:

[0085]

[0086] In the formula, η is the electrode overpotential; j0 is the current density at the electrode surface; α a and α cE represents the oxidation reaction transfer coefficient and the reduction reaction transfer coefficient, respectively; eq,i Represents the equilibrium potential; k0 is the reaction rate constant; c s,max and c s,surf These are the maximum lithium-ion concentration in the active material particles and the lithium-ion concentration on the surface of the active particles, respectively.

[0087] Thermal model equations:

[0088] ;

[0089] In the formula, ρ is density, and C p is the specific heat capacity, k is the thermal conductivity, and Q is the total heat generated by the battery.

[0090] Based on the heat generation method, the total heat generated by the battery (Q) It consists of three parts: heat of reaction (Q) rea ), polarization heat (Q) act ) and Ohm heat (Q ohm The heat of reaction is a reversible heat (Q). rev Polarization heat and ohmic heat are irreversible heats (Q). irr Their expressions are as follows:

[0091]

[0092]

[0093] In the formula, к eff D ΔS represents the effective diffusion conductivity, n is the lithium ion charge number, and ΔS represents the entropy change before and after the chemical reaction. Ohmic heat mainly considers the positive and negative electrodes and the electrolyte.

[0094] When there is heat convection between the battery surface and the external environment, the boundary conditions of the thermal model are:

[0095]

[0096] In the formula, T amb is the ambient temperature, and h is the convective heat transfer coefficient between the battery surface and the external environment.

[0097] Since many parameters are sensitive to temperature and are believed to follow Arrhenius's law, the values ​​of these parameters can be expressed as:

[0098]

[0099] In the formula, Φ and Φ ref The parameter values ​​E are the current and reference temperatures, respectively. act For its corresponding activation energy, T refFor reference temperature, this embodiment is set to 293 K.

[0100] (3) Using the electrochemical-thermal coupled model constructed with COMSOL, the boundary conditions and initial conditions of each physical model were set according to the actual simulation requirements of lithium metal, the mesh was generated, and the solution calculation was performed, such as... Figure 3 As shown.

[0101] The initial and boundary conditions of the electrochemical model are as follows: the initial lithium concentration in the electrolyte is 2000 mol / m³. 3 The initial concentration of lithium ions in the positive electrode is 4000 mol / m 3 The negative electrode tab ends at the ground boundary, and the initial boundary potential of the positive electrode tab ends is 4.4 V. Due to limitations in simulation technology, only the internal short circuit caused by lithium dendrites is studied. In this case, the lithium dendrites only serve as electrical connections and do not penetrate the overall battery structure. The lithium dendrite radius is set to 150 μm, and the length is equal to the separator thickness. It is worth noting that the lithium dendrites in this example do not pierce the separator; they only connect the positive and negative electrodes, forming a positive-negative short circuit. The method for setting the lithium dendrites is as follows: Figure 3 As shown in (a).

[0102] The initial and boundary conditions of the thermal model are as follows: the initial temperature of the thermal model is 293 K.

[0103] Mesh generation was performed. The model includes: positive current collector, positive electrode, separator, negative electrode, negative current collector, and lithium dendrites. First, the contact surfaces of the lithium dendrites with the positive and negative electrodes were meshed using the same mesh. Then, the lithium dendrite region was refined using a free tetrahedral mesh. Finally, the remaining areas of the model were meshed using a free tetrahedral mesh. Since the fixed geometry includes 8 domains, 46 boundaries, 84 edges, and 48 vertices, the model consists of 10069 domain elements, 4864 boundary elements, and 428 edge elements. Therefore, the final mesh generation diagram is as follows. Figure 3 As shown in (b).

[0104] (4) Based on the three-dimensional electrochemical-thermal coupling model, the method of studying the internal short circuit of lithium metal battery was used to analyze the changes in the internal short circuit characteristics of lithium dendrites with a radius of 150 μm, including electrode current density, voltage, battery temperature rise and internal heat generation.

[0105] After triggering an internal short circuit, lithium dendrites pierce the separator to form a conductive path, such as... Figure 4 As shown, due to the strong locality of the short circuit location and the relatively small short-circuit current compared to the battery capacity, the battery voltage did not drop to zero; instead, it rapidly decreased from 4.23V to 3.6V within 0.1 s. Accompanying this voltage drop, the electrode current density reached a peak of 8.8 × 10⁻⁶ at 0.08 s. 6 A / m 2The peak current occurs at 0.8 s, significantly lagging behind the voltage drop phase. This lag stems from the coupling effect of electricity, heat, and ion transport during the internal short circuit: initially, the battery potential difference drives electrons to flow rapidly through dendrite channels, causing a sharp voltage drop; subsequently, the generated Joule heating raises the local temperature at the short circuit point, potentially causing local melting of lithium dendrites or thermal decomposition of the SEI film and separator, thereby reducing contact resistance and expanding the effective conductive area, allowing the current to continue increasing even after the voltage has decreased, until it reaches its peak. After the peak, the current gradually decays and tends to stabilize, mainly due to the continued discharge leading to a further decrease in the overall battery voltage, weakening the driving force, and the concentration polarization caused by the rapid consumption of lithium ions near the positive electrode, which limits the electrochemical reaction rate.

[0106] Figure 5 Simulation results of the heat generation characteristics of lithium metal batteries after a lithium dendrite-triggered internal short circuit are presented. Among them, Figure 5 The change in heat production rate in (a) shows that in the initial stage from 0 to 0.2 s, due to the sharp increase in current density at the short-circuit channel, Joule heat accumulates rapidly, and the heat production rate increases sharply to a peak of approximately 4.5 × 10⁻⁶. 10 W / m 3 Subsequently, as the battery voltage continued to decrease and ion transport tended to reach equilibrium, the heat generation rate gradually declined and leveled off. Figure 5 (b) Further, the evolution of the total heat generation power of the battery as a whole and its components is presented: the total heat generation power initially reaches its peak and then continuously decreases, consistent with the trend of heat generation rate; the heat generation power of the positive and negative electrodes first increases and then decreases, mainly due to the combined effect of reaction heat and ohmic heat, and weakens as the short-circuit process stabilizes; the heat generation contribution of the current collector and lithium dendrites themselves is always close to zero, indicating that their ohmic heat is negligible, and the main heat generation in the short-circuit region is concentrated at the electrode-electrolyte interface. In summary, the internal short-circuit thermal evolution can be summarized as follows: lithium dendrites pierce the separator to form a low-resistance path, triggering a local Joule thermal burst; subsequently, the heat diffuses to the surroundings, and if the temperature rises to the decomposition threshold of components such as the SEI film and electrolyte, it will trigger exothermic side reactions, forming a positive feedback between Joule heat and chemical heat, and pushing the total thermal power of the system to its peak at about 0.8 s. This stage is the critical dangerous period for thermal runaway evolution; if the accumulation of heat and gas further triggers chain reactions such as separator melting and positive electrode decomposition, the battery will enter an irreversible thermal runaway state.

[0107] like Figure 6The figure shows a comparison between the average surface temperature of the battery and the average temperature at the short circuit point after an internal short circuit occurs. The internal short circuit process induced by lithium dendrites exhibits a significantly localized temperature response. Within the first 0.2 seconds after the short circuit occurs, the temperature at the short circuit point rises sharply from 25 °C to approximately 62 °C. This is mainly due to the rapid accumulation of Joule heat caused by the extremely high local current density, while the thermal conduction between the lithium dendrites and the electrode interface is impeded, causing heat to concentrate in the micro-region and triggering a burst of temperature increase. After 0.2 seconds, the temperature begins to decrease continuously and eventually stabilizes at around 32 °C. This is attributed to the subsequent decrease in short-circuit current density, the decay of heat generation rate, and the gradual diffusion of accumulated heat to the battery interior and surface, eventually leading to a temperature drop under thermal equilibrium. However, the battery surface temperature remains around 25 °C throughout the entire process, with only extremely slight fluctuations. This indicates that the heat generation from the short circuit is strictly confined to the micron-sized dendrite-pierced region and fails to be effectively transferred to the battery surface. This phenomenon of sudden internal heating and stable external temperature clearly reveals the nature of heat concentration due to local short circuits. It also reflects the battery's overall large thermal inertia and effective heat dissipation capacity, which together maintain the stability of the surface temperature.

[0108] (5) Based on the construction method of the model, the radius of the lithium dendrites is changed and compared with the model while keeping other parameters unchanged. Figure 7 The voltage changes during the internal short circuit process of the battery under different lithium dendrite radii are shown. Under all conditions, the voltage continuously decreases from an initial value of approximately 4.23 V, eventually stabilizing around 3.6 V, reflecting the basic principle that lithium dendrites penetrate the separator, initiating an internal short circuit, leading to continuous battery discharge and a gradual voltage decrease. Analysis shows that, under the same conditions, as the lithium dendrite radius increases, its resistance decreases accordingly, while the short-circuit current increases. However, for the positive-to-negative electrode type internal short circuit, the influence of dendrite radius on the voltage decrease trend is relatively limited, only showing a slight increase in the voltage decrease when the radius is larger. The voltage curves under different radii generally exhibit a consistent decreasing behavior, indicating that in this type of internal short circuit mechanism, the voltage response is mainly dominated by the short-circuit discharge process and is not sensitive to changes in dendrite size.

[0109] Figure 8 The temperature evolution and cumulative heat generation during the internal short circuit process are shown under different lithium dendrite radii. Figure 8 (a) shows that the temperature rises rapidly to the peak value under all operating conditions and then gradually stabilizes; as the lithium dendrite radius increases, the corresponding peak temperature also gradually increases. Figure 8(b) shows that the total cumulative heat generation increases significantly with increasing dendrite radius. For example, when the radius increases from 50 μm to 150 μm, the cumulative heat generation increases dramatically from 0.029 J to 0.209 J. This phenomenon is due to the increased conductive cross-sectional area of ​​the short-circuit channel as the lithium dendrite radius increases, enhancing the conductivity of the short-circuit channel, which leads to an increase in short-circuit current, heat generation rate, and heat generation duration. The combined effect is manifested as a longer high-temperature duration, an increase in peak temperature, and a significant increase in cumulative heat generation.

[0110] (6) Based on the construction method of the model, with other parameters unchanged, the internal short circuit situation at different positions of lithium dendrites is compared and analyzed.

[0111] Figure 10 The temperature change curves after a lithium dendrite internal short circuit occurs in different regions of the battery (top left, bottom left, center, bottom right, and top right) are shown. Overall, the temperature changes at all locations exhibit a similar two-stage characteristic: in the initial short circuit stage (0–0.1 s), the temperature surges from the initial ambient temperature of 25 °C to a peak of 62–64 °C, due to the intense heat generation caused by the high current density during the internal short circuit; subsequently, from 0.1 to 1.2 s, the temperature continuously decreases, stabilizing around 31 °C at approximately 1.2 s, reflecting a dynamic balance between heat generation decay and internal heat dissipation. The peak temperatures in each region are very close (62.7–63.7 °C), indicating that the heat generation in the initial stage of the internal short circuit has a wide range of influence, and the location difference has a limited modulating effect on the peak temperature. Further analysis reveals that the location of the internal short circuit has a subtle but identifiable influence on the details of the temperature evolution. When the internal short circuit occurs in the upper left region near the tab, the battery reaches its lowest peak temperature (approximately 62.70 °C) and a slightly lower stable temperature (approximately 31.05 °C). When the internal short circuit is located in the lower right region, both the peak temperature (approximately 63.76 °C) and the stable temperature (approximately 31.63 °C) are relatively higher. As the short circuit point moves from the center towards the lower left or lower right, the temperature also shows a slight upward trend. This phenomenon may stem from the strong heat dissipation conditions and current distribution characteristics near the tab: as a current convergence point, the heat generated in the vicinity of the tab is more easily dissipated through its high thermal conductivity, thus alleviating localized temperature rise. In contrast, areas farther from the tab (such as the lower right corner) have longer heat dissipation paths, resulting in a more pronounced heat accumulation effect and a slightly higher temperature. Nevertheless, the temperature difference between locations during the stable phase is small (31.0~31.4 °C), indicating rapid heat diffusion on a macroscopic scale and a relatively uniform overall heat distribution.

[0112] according to Figure 11The isosurface distribution of battery temperature at t=1.2 s shown can be used to further analyze the physical mechanism by which the location of the internal short circuit affects its thermal behavior. The temperature field as a whole exhibits a local high-temperature characteristic centered on the short circuit point, and decreases gradually towards the surrounding space. The temperature in the region far from the short circuit point is close to the initial ambient temperature of 24~25 °C, which indicates that the heat generation from the internal short circuit has a strong local concentration in space.

[0113] Significant differences can be found by comparing different locations: when the internal short circuit occurs at the geometric center of the battery, the high-temperature area is the most extensive, with the highest temperature reaching 36.23 °C, indicating that heat accumulation is more significant in the central area and is relatively uniformly transferred to the surrounding areas; while when the short circuit occurs at the edge (such as the upper left, lower left, upper right, and lower right), the high-temperature area is more limited to the vicinity of the short circuit point, with the highest temperature being about 35.56 °C. The overall temperature level is lower, reflecting that heat in the edge area is more easily dissipated to the outside of the battery or along the direction of the tabs, resulting in higher heat diffusion efficiency.

[0114] From the perspective of heat propagation paths and heat dissipation conditions, the central region, being inside the battery, experiences similar heat transfer distances in all directions, and its surrounding heat dissipation conditions are relatively symmetrical, resulting in better temperature uniformity. However, heat is not easily dissipated quickly, leading to a higher overall temperature rise and a larger high-temperature area. When the short-circuit point is near the edge, especially near the tabs, heat can be transferred along shorter paths to the battery boundary or the tabs of high-thermal-conductivity structures, enhancing heat dissipation and thus reducing the maximum temperature and the high-temperature range. It is worth noting that in areas near the edge but not near the tabs (such as the lower right), the heat dissipation path is still better than in the center, but not as good as in areas near the tabs; therefore, its temperature response falls between that of the center and the tab location.

[0115] In summary, the location of an internal short circuit primarily influences the heat transfer path and heat dissipation efficiency, thereby regulating the local temperature rise and spatial distribution of the high-temperature zone at the short circuit point. A central short circuit causes more widespread heat accumulation, while an edge short circuit exhibits more localized thermal characteristics. The area near the tabs, due to its superior heat dissipation, displays the mildest temperature response. This understanding provides guidance for battery thermal management design, suggesting that enhanced heat dissipation in the internal areas and regions far from the tabs should be emphasized during battery safety assessments.

[0116] (7) Based on the construction method of this model, with other parameters unchanged, the internal short circuits caused by changing the radius of the lithium dendrites and different positions of the lithium dendrites were compared and analyzed. The larger the radius of the lithium dendrites, the stronger the temperature non-uniformity inside the battery after the internal short circuit, and the higher the temperature peak reached, resulting in a significant increase in accumulated heat generation. The location of the internal short circuit mainly affects the spatial distribution of heat and the local heat dissipation efficiency. Internal short circuits occurring in the center of the battery have a wider heat accumulation range and better temperature distribution uniformity; internal short circuits occurring near the tab area show the mildest temperature rise response due to the better heat dissipation path; while internal short circuits occurring inside the non-tab edge area have relatively high local temperature rises, requiring more attention in safety design. This can provide theoretical guidance for preventing battery internal short circuit failure and subsequent thermal runaway.

[0117] Based on the simulation data obtained in Example 1, the following improvements can be made to the design of lithium batteries:

[0118] (1) Regarding material selection:

[0119] 1) Regarding diaphragm materials: Traditional simulation models often simplify the heat source to a fixed value or rely solely on voltage-current curves, failing to reproduce the dynamic evolution of localized rapid heating (rising to above 62 ℃ in 0.2 s) during an internal short circuit. They also cannot quantify the failure risk of diaphragms with different thermal stability under short-circuit scenarios, leading to material selection relying on trial and error and making it difficult to accurately match safety requirements. This invention, based on simulation data from Example 1 showing a rapid temperature rise from 25 ℃ to 62 ℃ within 0.2 s at the short-circuit point, with even higher peak values ​​and close to the diaphragm decomposition threshold (80 ℃) in large-radius dendrite scenarios, should prioritize diaphragm materials with high pore-closing temperature and high melting point to ensure no failure under the initial localized high temperatures of a short circuit. Simultaneously, a high-temperature resistant coating can be applied to the diaphragm surface to enhance resistance to dendrite penetration.

[0120] 2) Regarding electrolyte and SEI film optimization: Existing models cannot reveal the quantitative relationship between dendrite growth location and short-circuit risk. They can only qualitatively determine that the risk is higher in the edge region, but cannot clearly identify the temperature differences of short circuits at different locations and the high-risk areas for lithium deposition. Therefore, they cannot provide targeted design suggestions for electrolyte additives and SEI films, and it is difficult to actively guide lithium deposition to a safe area. Based on Example 1, this invention confirms through multi-location simulation that when lithium dendrites grow at the electrode edge, far from the tab, the peak short-circuit temperature (31.63 ℃) is higher than that near the tab (31.05 ℃), and the short-circuit heat accumulation range in the central region is wider. Based on this, electrolyte additives can be optimized or artificial SEI films can be designed to induce lithium deposition to preferentially occur in the transition region with uniform current distribution and good heat dissipation, avoiding nucleation growth in high-risk areas.

[0121] 3) Regarding electrode and current collector materials: Existing models cannot quantify the correlation between material conductivity, thermal conductivity, and local heat generation. They can only macroscopically determine that high conductivity materials can reduce ohmic heat, but cannot accurately identify the impact of the conductivity difference between the positive and negative electrodes on the short-circuit current distribution, resulting in a lack of refined basis for material selection. However, this invention, combined with simulation data from Example 1 showing that the solid-phase conductivity of the positive electrode is much higher than that of the negative electrode and that the current collector conductivity directly affects the current distribution, suggests that high conductivity types can be prioritized for the positive electrode to reduce solid-phase ohmic heat. The current collector material needs to balance high conductivity (uniform current) and high heat dissipation (exhausting local heat) to avoid heat concentration caused by an imbalance in a single parameter.

[0122] (2) In terms of structural optimization:

[0123] 1) Regarding the adjustment of the position and number of tabs: Traditional models can only provide macroscopic current distribution trends and cannot accurately capture the quantitative correlation between tab position and heat dissipation efficiency and current convergence. They also cannot clearly define the impact of different tab layouts on short-circuit temperature, leading to tab design relying heavily on empirical adjustments and making it difficult to eliminate heat dissipation blind spots. Based on simulation data from Example 1, this invention shows that the short-circuit temperature peak is lowest near the tabs (62.70 ℃), while the temperature is highest in the edge region far from the tabs (63.76 ℃). The core reason is that tabs can shorten the heat dissipation path and improve thermal conductivity. Based on this, the number of tabs can be increased (e.g., from 2 to 4) or the tab position can be adjusted to cover heat dissipation blind spots such as the lower right and lower left, balancing current distribution and reducing current convergence dead zones.

[0124] 2) Current collector structure optimization: Existing models cannot accurately identify high current density regions inside the battery, nor can they quantify the correlation between current collector thickness, conductivity, and local ohmic heat. This leads to a bias towards overall reinforcement in current collector structure design, resulting in material waste and an inability to specifically address local heat generation issues. Based on the simulation conclusion in Example 1 that high current density regions are prone to local ohmic heat generation, this invention can increase the current collector thickness or use materials with higher conductivity in high-risk regions identified in the simulation (such as electrode edges and regions far from the tabs) to reduce local ohmic heat. At the same time, the current collector mesh shape (such as honeycomb) is optimized to balance the current distribution.

[0125] 3) For electrode edge protection: Existing models cannot quantify the short-circuit risk at the electrode edge (especially near the non-tab), and cannot clearly define the impact of coating type (high resistance / high thermal conductivity) on short-circuit current and temperature, resulting in a lack of scientific basis for edge protection design and difficulty in effectively blocking high-risk short-circuit channels; Embodiment 1 of this invention confirms that the electrode edge (near the non-tab) is a high-risk area for short circuits, with low equivalent resistance, high current and long heat dissipation path. Based on this, a high-resistance coating can be applied to this area to limit the short-circuit current amplitude, or a high-thermal-conductivity coating can be applied to quickly diffuse local hot spots.

[0126] (3) In terms of thermal management design:

[0127] 1) Designing Local Heat Dissipation Structures: Traditional thermal management models often focus on overall heat dissipation efficiency, failing to reveal the localized heat concentration characteristics of internal short-circuit heat generation (e.g., micron-level high temperatures at the short-circuit point and widespread heat accumulation in the central region). They also cannot quantify the effects of different local heat dissipation structures on short-circuit temperature regulation, making it difficult for thermal management designs to cover high-risk areas. Simulation results from Example 1 show that the central region has the widest short-circuit high-temperature coverage (up to 36.23 ℃), while the non-tab edge region experiences localized temperature increases. Based on this, a micro-thermal conductive channel (such as high thermal conductivity fiber) can be added to the center of the battery, and thermal pads can be added to the non-tab edge region to shorten the heat dissipation path.

[0128] 2) Overall Heat Dissipation Optimization: Existing models fail to detect the contradictory characteristics of internal rapid heating (short circuit point 62 ℃) and stable surface temperature (25 ℃), and cannot quantify the correlation between surface convective heat transfer coefficient and internal heat dissipation. This leads to an over-reliance on increasing the heat dissipation area in the overall heat dissipation design, ignoring the internal-to-surface heat transfer bottleneck. As revealed in Example 1, short-circuit heat generation is confined to the micron-level dendritic region, and the battery surface temperature shows almost no fluctuation, reflecting strong surface heat dissipation capacity but difficulty in dissipating internal heat. Based on this, the battery casing material (such as high thermal conductivity aluminum alloy) or the addition of heat dissipation fins can be optimized to improve the convective heat transfer coefficient between the surface and the environment; at the same time, the heat dissipation surface of high-risk areas should be avoided when stacking batteries to ensure rapid heat dissipation.

[0129] (4) In terms of failure protection and early warning:

[0130] 1) Design a short-circuit protection structure to block high-risk short-circuit channels: Existing models cannot clearly identify the key feature that the dendrite-to-positive and negative electrode contact surface is the core of heat generation, and cannot quantify the impact of protection structures (such as self-healing coatings) on the contact area and short-circuit current. This results in a lack of targeted protection structure design and difficulty in effectively blocking short-circuit channels. Simulations in Example 1 confirm that the dendrite-to-positive and negative electrode contact surface is the core of heat generation. The larger the contact area (the larger the dendrite radius), the more concentrated the heat generation. Based on this, a self-healing coating can be applied to both sides of the diaphragm to quickly block the short-circuit channel when the dendrite pierces through, reducing the contact area. At the same time, a micro-isolation layer is set in high-risk areas (edges and centers) to prevent direct short circuits between the positive and negative electrodes after dendrite piercing through.

[0131] 2) Design an early warning mechanism: Existing models cannot obtain the failure precursor characteristics of internal short circuits (such as voltage drop rate and local temperature rise rate), and can only judge failure based on the final voltage or surface temperature. This results in a delayed response and high false alarm rate in the early warning mechanism, making it impossible to avoid risks in advance. Based on the dynamic data in Example 1, where the voltage drops from 4.23 V to 3.6 V within 0.1 s after an internal short circuit and the local temperature rises by 37°C within 0.2 s, a voltage monitoring module can be embedded. A voltage drop rate threshold (e.g., 0.6V / 0.1 s) can be set to trigger an early warning. At the same time, a miniature temperature sensor can be built into the high-risk area to monitor the local temperature rise rate (e.g., 30°C / 0.2 s) and activate heat dissipation or power-off protection in advance.

[0132] In summary, although Example 1 focuses on a specific lithium metal battery, the three-dimensional parameterized dendrite-multiphysics coupled simulation framework established in this invention has methodological universality. After adaptive adjustments, it can provide a more accurate research direction for battery design and adjustment through simulation results, reduce a large number of repeated experiments, shorten the R&D time for battery design and adjustment, and can also be accurately used to study other novel battery systems with similar internal short-circuit mechanisms (such as dendrite growth).

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A three-dimensional electrochemical-thermal coupling simulation system for internal short circuits in lithium metal batteries, characterized in that, The three-dimensional electrochemical-thermal coupled simulation system includes: A three-dimensional geometric model is established based on the parameters of the lithium metal battery sample to be tested. The three-dimensional geometric model includes the positive electrode, negative electrode, separator, and current collector of the battery. The lithium dendrite geometry embedded in the three-dimensional geometric model and used to simulate physical short-circuit contacts has a radius and spatial position that can be defined parameters. The electrochemical-thermal coupled calculation module is used to couple the following processes: Electrochemical process: Calculate the voltage and current distribution and electrochemical heat generation of the lithium metal battery under test; Thermal processes: Calculation of the spatiotemporal evolution of the temperature field of lithium metal batteries driven by both electrochemical heat generation and internal short-circuit ohmic heat; Short-circuit feedback process: The internal electrochemical parameters of the lithium metal battery that change due to temperature changes are fed back to the electrochemical process in real time, and the internal short-circuit resistance and its heat generation are fed back to the electrochemical process and the thermal process. The three-dimensional electrochemical-thermal coupling simulation system simulates and outputs data on changes in battery voltage, current density, temperature field, and heat generation power under different internal short-circuit scenarios by changing the radius and position parameters of lithium dendrite geometry. This data is used to analyze internal short-circuit characteristics and guide battery safety design.

2. The three-dimensional electrochemical-thermal coupled simulation system according to claim 1, characterized in that, In the electrochemical-thermal coupling calculation module, temperature changes affect the electrochemical reaction kinetic parameters in real time through the Arrhenius relation, realizing the bidirectional coupling of the thermal field and the electrochemical field.

3. The three-dimensional electrochemical-thermal coupled simulation system according to claim 1, characterized in that, The radius parameter of the lithium dendrite geometry ranges from 50 μm to 150 μm, and the position parameter is selected from one of a plurality of preset positions within the battery plane.

4. The three-dimensional electrochemical-thermal coupled simulation system according to claim 1, characterized in that, The parameter initialization and calibration of the three-dimensional geometric model and the electrochemical-thermal coupling calculation module are based on data obtained from electrochemical and thermal tests on real lithium metal battery samples, electrode samples and material samples to be tested. The data includes one or more of the following: geometric parameters, solid / liquid phase conductivity, lithium ion diffusion coefficient, reaction rate constant, specific heat capacity and thermal conductivity.

5. The three-dimensional electrochemical-thermal coupled simulation system according to claim 1, characterized in that, When meshing a target region containing lithium dendrite geometry, the meshing strategy is as follows: first, perform consistent meshing on the contact surfaces between the lithium dendrite geometry and the positive and negative electrodes, and then refine the entire target region with free tetrahedral meshes.

6. A method for simulating the internal short-circuit behavior of a lithium battery using the three-dimensional electrochemical-thermal coupling simulation system according to any one of claims 1 to 5, characterized in that, Includes the following steps: Step 1: Obtain the physicochemical parameters of a real lithium battery sample, and initialize the parameters of the three-dimensional electrochemical-thermal coupling simulation system accordingly; Step 2: Define the initial radius and initial spatial position parameters of the lithium dendrite geometry in the three-dimensional electrochemical-thermal coupling simulation system, run the simulation system, and obtain simulation data under the initial internal short circuit scenario; Step 3: Change the radius and / or spatial position parameters of the lithium dendrite geometry, run the simulation system, and obtain simulation data for at least one modified internal short-circuit scenario; Step 4: Compare and analyze the simulation data obtained in Step 2 and Step 3 to evaluate the risk level of internal short circuit caused by lithium dendrite geometry under different parameters.

7. A lithium battery safety design method, characterized in that, The hazard level and parameters obtained by the method according to claim 6 are used to optimize the lithium battery.

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